Tesla has quietly developed a new hardware suite with more computing power to help achieve its goal of full automation, according to Electrek. The updated onboard computer, dubbed “HW 2.5,” would seem to contradict the previous vow by Tesla CEO Elon Musk that all vehicles released since October 2016 would have the hardware necessary to achieve “full self-driving capabilities.”

Last year, Musk promised that once Tesla’s Autopilot system had accumulated enough real-world telemetry and data, the company would push out an over-the-air software update to all Tesla vehicles to enable full autonomy. The announcement conjured up a fantastical vision of Musk flipping a switch to suddenly transform all of the Tesla vehicles on the road into self-driving robots. Now it appears that Tesla is hedging its bets by holding this new hardware suite in the wings in the off-chance its current system proves inadequate.

On its website and in its dealerships, Tesla offers the option of “full self-driving capability” for $48 a month or $4,000 after delivery for the Model S. “Please note that Self-driving functionality is dependent on extensive software validation and regulatory approval, which may vary widely by jurisdiction,” the automaker notes on its website.

Tesla’s “full self-driving capability” option on its website.

In a statement, a Tesla spokesperson confirmed the existence of HW 2.5, but played down its significance. “The internal name HW 2.5 is an overstatement, and instead it should be called something more like HW 2.1,” the spokesperson said. “This hardware set has some added computing and wiring redundancy, which very slightly improves reliability, but it does not have an additional Pascal GPU.”

He added that all new Model S, X, and 3 vehicles ordered today will be delivered with the new hardware suite, and promised to upgrade any current HW 2.0-equipped Tesla on the road today with HW 2.5 if full autonomy is unachievable.

“However, we still expect to achieve full self-driving capability with safety more than twice as good as the average human driver without making any hardware changes to HW 2.0,” the spokesperson said. “If this does not turn out to be the case, which we think is highly unlikely, we will upgrade customers to the 2.5 computer at no cost.”

Let’s take a step back and remember what Tesla promised last year:

We are excited to announce that, as of today, all Tesla vehicles produced in our factory – including Model 3 – will have the hardware needed for full self-driving capability at a safety level substantially greater than that of a human driver. Eight surround cameras provide 360 degree visibility around the car at up to 250 meters of range. Twelve updated ultrasonic sensors complement this vision, allowing for detection of both hard and soft objects at nearly twice the distance of the prior system. A forward-facing radar with enhanced processing provides additional data about the world on a redundant wavelength, capable of seeing through heavy rain, fog, dust and even the car ahead.

Now it appears that at least some of these vehicles won’t have all the “hardware needed,” and will need to be taken to Tesla service centers for upgrades. It’s unclear how widespread this will be because Tesla’s Autopilot software isn’t ready for full automation.

“Full self-driving capability” can mean a lot of things, but it most likely refers to Level 4 automation as defined by SAE International, which is defined as “high automation.” That means it’s a car capable of driving in any road or weather condition without any human intervention. Last year, Musk said the hardware is fully capable of “Level 5 autonomy,” which most experts agree is still theoretical at best.

Naturally, the revelation of HW 2.5’s existence has led some critics to cast doubt over Musk’s original promise.

Looks like pretty solid evidence that Tesla’s Hardware 2 suite was not capable of Level 4/5 as promised. Why upgrade it if it was? https://t.co/lms9q5tjcF

But Tesla insists that the hardware upgrade will be minor at best, and that the core camera-and-sensor suite — eight cameras with 360-degree viewing at up to 820 feet of distance, as well as 12 ultrasonic sensors that can detect both hard and soft objects — will still prove valid. Tesla is breaking with its competitors in the self-driving space by declining to include LIDAR sensors under the assumption the equipment will be too expensive for personal ownership. Musk has said previously that LIDAR sensors “don’t make sense in a car context.”

We’ll get a better sense of Tesla’s self-driving capabilities at the end of the year when the company will demonstrate a coast-to-coast autonomous journey. “We reiterate our goal of driving from a parking lot in downtown LA to a parking lot in downtown NY without touching the controls by the end of the year,” the spokesperson said.